For example, methods described in Patent Literature 1, Patent Literature 2, and Patent Literature 3 are known as the production methods of 2-acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione.
In Patent Literature 1, Li et al. obtain 3-bromo-3-buten-2-one by brominating 3-buten-2-one with bromine, followed by dehydrobromination using DBU (diazabicycloundecene). They report a method of subsequently performing a coupling reaction of 3-bromo-3-buten-2-one and 2-hydroxy-1,4-naphthoquinone with additional DBU added, and then obtaining a solid by crystallization to crystallize the obtained solid, thereby obtaining 2-acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione.
In Patent Literature 2, Li et al. obtain 3-bromo-3-buten-2-one by brominating 3-buten-2-one with bromine, and then performing dehydrobromination using DBU. Subsequently, 3-bromo-3-buten-2-one and 2-hydroxy-1,4-naphthoquinone are coupled with DBU, and a crude mixture of 2-acetyl-4H,9H-naphtho[2,3-b]dihydrofuran-4,9-dione and 2-acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione is obtained by crystallization. This crude mixture is oxidized with manganese dioxide to obtain 2-acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione, which is then treated with ethyl acetate to obtain 2-acetyl-4H,9H-naphtho [2,3-b]furan-4,9-dione.
In Patent Literature 3, Jiang et al. obtain 2-acetyl-4H,9H-naphtho[2,3-b]dihydrofuran-4,9-dione by brominating 3-buten-2-one with bromine, and performing dehydrobromination with DBU to obtain 3-bromo-3-buten-2-one, and then adding 2-hydroxy-1,4-naphthoquinone into the reaction system, followed by condensation under an air atmosphere. Subsequently, 2-acetyl-4H,9H-naphtho[2,3-b]dihydrofuran-4,9-dione is stirred under an air atmosphere with DBU to obtain 2-acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione.
All of these production methods have a low yield, and they are not recognized as methods that can efficiently produce target substances in an industrial scale.